Add 6 ounces raspberries, blueberries, blackberries, sugar, and lemon juice to medium bowl. Stir well to incorporate. Allow the berry mixture to sit at room temperature for 30 minutes.
Add 6 ounces of raspberries to a food processor along with 2 tablespoons sugar. Puree until smooth. Remove the raspberry puree to a bowl, cover with plastic wrap, and let chill in the refrigerator.
Whip the heavy cream with a hand mixer until frothy and thick. Add the sugar and continue to beat until medium peaks appear. Gently fold in the raspberry puree until blended.
To serve, add a spoonful of the heavy cream to the bottom of an old fashioned glass, top with a spoonful of fruit, and sprinkle with a handful of granola. Repeat the layering once more. Top with a small spoonful of the cream and a few berries on top. Repeat with the remaining glasses and ingredients.